1. Technical Field
Embodiments of the present invention relates to a sheet separation/conveyance device for separating and conveying a sheet such as an original document and a recording medium, and an image forming apparatus including the sheet separation/conveyance device.
2. Related Art
Image forming apparatuses include printers, copiers, facsimile machines, and multifunctional digital machine including at least two functions of the printers, the copiers, and the facsimile machines. These image forming apparatuses feed a sheet of paper including an original document, a recording paper, a transfer sheet, a printing sheet and the like from a sheet container. As the sheet travels in an image forming device, an image is formed on a surface of the sheet, and then the sheet is discharged from the image forming apparatus. The sheet container includes a sheet feeding device and the image forming device includes a sheet conveying device.
Known sheet conveying device employs an electrostatic attraction system including an endless electrostatic attraction belt. A base of the endless electrostatic attraction belt is a belt-shaped flexible insulating member formed by rubber, resin, or the like. Multiple sheet-like electrodes (electrode patterns) are embedded in the base of the endless electrostatic attraction belt. The endless electrostatic attraction belt is wound around multiple rollers to rotate and convey the sheet.
Such an electrostatic attraction system is employed in Japanese Patent Application Publication Nos. JP-05-139548-A and JP-2003-237960-A, for example.
JP-05-139548-A discloses a sheet conveying device that sequentially picks up an uppermost sheet of a sheet stack accumulated in a sheet container of an image forming apparatus. The sheet conveying device applies an alternative charge to a conductive endless belt wound around multiple rollers, so that the belt swings or rotates to contact or nearly contact the accumulated sheet stack. After the uppermost sheet is attracted to and held by the belt, the belt is moved to separate from the sheet stack. By so doing, the sheet is separated from the sheet stack.
Further, a sheet conveying device of the electrostatic attraction system disclosed in JP-2003-237960-A includes a surface potential meter that measures a quantity of electric charge on the belt so as to include a physical property detection unit to detect a physical property of the sheet to be fed, a charge forming unit to form an electric charge on an attraction surface, and a controller to control a quantity of electric charge generated by the charge forming unit and a time of attraction during which a sheet contacts the attraction surface.
However, the conventional sheet conveying device using electrostatic attraction as disclosed in JP-2003-237960-A uses a measuring instrument such as an electrometer on the belt to detect a charged condition such as a quantity of electric charge on the belt. This configuration requests wide space around the belt and causes a large amount of cost.